WASHINGTON — Senate Democrats' campaign arm again outraised its Republican rival last month and borrowed $5.2 million to buy a Capitol Hill home next to its headquarters, according to campaign finance reports filed Friday.

Both campaign groups' fundraising summaries showed donors were continuing to open wallets. Democrats are defending a narrow majority, and strategists from both parties say Republicans have a shot at picking up the six seats they need to claim that status for the first time since 2006's elections.